This program is aimed at development of instrumentation and procedures for detection and localization of occult by fluorescence endoscopy using a violet laser, fiberoptic endoscope and image intensifier, following intravenous injection of the tumor-specific fluorescent dye hematoporphyrin. Clinical tests will be performed to localize bronchogenic tumors at the carcinoma in situ stage, and to investigate the feasibility of diagnosis of GI tract cancer. Photoradiation therapy with hematoporphyrin and the violet laser will be investigated in animals. Measurements will be made of hematoporphyrin content in malignant tumors and in normal tissues, and violet light dosimetry methods and instrumentation will be developed as a prelude to photoradiation therapy in humans at a later time.